Whey protein preparation method

Abstract

The present invention relates to a whey protein preparation method. The method comprises: a hydrolysis step and an enzyme deactivation step. In the hydrolysis step, hydrolysis of a whey protein solution is carried out in the presence of an enzyme, the hydrolysis temperature is 55°C or below, the hydrolysis time is 60 min or less, and the temperature of thermal history of the whey protein solution before the hydrolysis does not exceed 40°C; and before the hydrolysis is completed, lactose is added to a system comprising a whey protein hydrolysis component, wherein the addition amount of the lactose is 15% to 300% by mass of the content of the whey protein. In the enzyme deactivation step, after the hydrolysis is completed, the pH value of a hydrolysate solution is adjusted to 7.2-8.0 and then enzyme deactivation by heating is carried out.

Description

Whey protein preparation method Technical Field The invention belongs to the field of food and relates to a method for preparing a protein product, in particular to a method for processing and preparing whey protein. Background Art Cow's milk is the main raw material for producing infant formula and is also one of the first allergens that infants and young children come into contact with. Food protein allergy is an inappropriate immune response of infants to protein in food. Infants' early food is mainly milk, so milk protein allergy is the most common food protein allergy in infants after birth. The incidence of infant milk protein allergy is 2% to 6%, and clinical manifestations include angioedema, urticaria, atopic dermatitis, respiratory symptoms, diarrhea, vomiting, intestinal colic, etc. Cow's milk contains more than 20 kinds of proteins, all of which are potentially allergenic, but it is generally believed that β-lactoglobulin is the main allergen, and β-lactoglobulin mainly exists in whey protein. Therefore, the content of β-lactoglobulin can be reduced by hydrolyzing whey protein. Hydrolyzed whey protein is composed of amino acids, oligopeptides and polypeptides, and is a pre-digested protein. The hydrolyzed whey protein reduces the antigenicity of milk protein. The higher the degree of hydrolysis, the lower the antigenicity. Moderate hydrolysis of whey protein can induce infants to develop tolerance to milk protein. Hydrolyzed whey protein is widely used in special medical formula foods, sports foods and health foods due to its low allergenicity, easy digestion, no residue and rich in bioactive peptides. At present, the main method to reduce the content of β-lactoglobulin in the industry is through biological enzymatic hydrolysis technology, such as: Reference 1 discloses a method for reducing beta lactoglobulin in concentrated whey protein powder by using biocomposite enzyme hydrolysis. The method comprises dissolving concentrated whey protein powder with a mass ratio of 1.6-5.0% in water, keeping the mixture at 50-100°C for 20-60 minutes, and then cooling the mixture to 45°C; subsequently, adding the concentrated whey protein powder and the composite enzyme to the whey protein solution at a mass ratio of 40-80:1, and performing enzymolysis at 30-45°C for 3-8 hours; after the enzymolysis is completed, sterilizing the feed liquid, controlling the sterilization temperature at 100-125°C, and keeping the mixture for 90-180 seconds; concentrating the feed liquid after sterilization, controlling the concentration temperature at 50-85°C, and achieving a solid content concentration of 20-35% after concentration; and finally spray drying the concentrated solution, with the hot air inlet temperature at 200-210°C, the temperature at 80-90°C, and the feed liquid temperature at 65-75°C. Reference 2 discloses a partially hydrolyzed whey protein powder and a preparation method thereof, wherein concentrated whey protein is prepared into a 5% to 10% whey protein aqueous solution, which is kept at 55°C to 85°C for 5 to 10 minutes to denature the protein, and then the aqueous solution is cooled to the hydrolysis temperature, and a complex is added according to a protease to whey protein mass ratio of 0.4 to 0.9:100. The invention discloses a composite protease, which is hydrolyzed at 50-55°C for 2-4 hours, wherein the composite protease is a mixture of neutral protease F and neutral protease G, or neutral protease F and neutral protease P, in a mass ratio of 3-8:1; after the hydrolysis is completed, the pH value of the solution is adjusted to 6.7-6.9, and the enzyme is inactivated by heat treatment at 80-95°C for 5-10 minutes to terminate the hydrolysis reaction; the solution after the hydrolysis reaction is terminated is concentrated by nanofiltration, and the solid content after concentration is 20%-35%; the concentrated solution is spray-dried, and the temperature of the feed liquid during feeding is 20-25°C, and the hot air inlet temperature is 135-175°C. In addition, there are other processes for pre-modification of whey protein. For example, Reference 3 also provides a method for producing a modified whey protein with improved thermal stability without using additives such as organic solvents, and the modified whey protein produced by the method. The production method is to contact and mix a whey protein solution with a whey protein solution that is rotated into a thin film cylinder and flows, and to heat the whey protein solution at a temperature in the range of 76 to 120°C for 5,000 seconds. -1 ~25,000s -1 The shear rate was 8 minutes to 0.1 seconds. However, its effect on hydrolyzed whey protein was not discussed. Although the above attempts have been made in the prior art for processing whey protein, there is still room for further improvement in providing a whey protein product with higher efficiency and better quality. References: Reference 1: CN 102940126 A Reference 2: CN 107136295 A Reference 3: CN 101959423 A Summary of the invention Problem that the invention aims to solve As mentioned above, in the prior art, considering that spray drying is a common method for preparing the final hydrolyzed whey protein powder, and the process requires heating the whey protein system to above 100°C or even higher, although the time is short, there is still concern about thermal denaturation of the protein component, which is prone to increase in viscosity and gelation, thereby reducing nutritional value and usability. Therefore, pre-modification treatment is used when hydrolyzing whey protein to reduce the adverse effects on protein components during spray drying. However, it has been found in long-term practice that one of their disadvantages is that the pre-modification treatment time is long. For example, the denaturation treatment of the concentrated whey protein solution in the early stage of the reference 1 is carried out by keeping it at 50°C to 100°C for 20-60 minutes. Similarly, in the reference 2, the whey protein aqueous solution is kept at 55°C to 85°C for 5 to 10 minutes to denature it. This will increase energy consumption in the production process, prolong production time, and from the perspective of microbial control, it is not conducive to the control of thermophilic bacteria. The second disadvantage is that the heat treatment denaturation of the whey protein solution will destroy the molecular structure of the whey protein and reduce the solubility. It is not conducive to enzymatic hydrolysis, and denatured protein particles are easily produced during enzymatic hydrolysis. Therefore, to achieve the target hydrolysis degree and molecular weight distribution, the hydrolysis time will be extended. The hydrolysis time of cited document 1 is 3 to 8 hours, and the hydrolysis time of cited document 2 is 2 to 4 hours. Long-term hydrolysis will inevitably lead to increased energy consumption and extended production cycle. The increase in insoluble particles will also lead to undesirable deposition on the membrane surface during the concentration process, resulting in reduced concentration efficiency. The third disadvantage is that the solid content after concentration is less than 35%. The low-solid content liquid is spray-dried, the granulation particle size is small, the product yield is low, the product preparation and spray drying consume more energy, and the production capacity is low. In addition, some other whey protein modification methods have been proposed, such as that in Reference 3, but they are not directed to hydrolyzed whey protein. At the same time, it still needs to undergo a relatively high heat treatment temperature during the pre-modification treatment. In view of the above-mentioned prior art problems, the primary purpose of the present invention is to provide a preparation method of hydrolyzed whey protein, in the method of the present invention, no pre-denaturation treatment is carried out on the whey protein aqueous solution, after the whey protein is fully hydrated, it is hydrolyzed at a certain temperature, and the hydrolysis time is shortened to within 60min, and the present invention adopts lactose and whey protein to carry out glycosylation cross-linking, and the protein thermal stability is improved, and further, pH protection is adopted in the enzyme inactivation process of the present invention, and the pH of the enzymolysis solution is adjusted to within the range of 7.2 to 8.0, and the enzyme inactivation ensures that the enzymolysis solution state is uniform and consistent, without denaturation. In addition, glycosylation modification can improve protein solubility, and the concentrated solution solid content can reach 35 to 45%, and the obtained product particle size is larger, and the dilution is good, and the production capacity is larger, and the energy consumption is lower. Furthermore, the present invention also aims to provide a method for preparing infant formula milk powder, which comprises or uses the method for preparing hydrolyzed whey protein provided by the present invention. Solutions for solving problems It has been found that the above technical problems can be solved by implementing the following technical solutions: [1]. The present invention first provides a method for preparing a whey protein product, wherein the method comprises: The hydrolysis step and the enzyme inactivation step, in, In the hydrolysis step, the whey protein aqueous solution is hydrolyzed in the presence of an enzyme, the hydrolysis temperature is below 55° C., and the hydrolysis time is below 60 min. Furthermore, the whey protein aqueous solution is subjected to a heat treatment temperature not exceeding 40° C. before hydrolysis. Before the hydrolysis is completed, lactose is added to the system including the whey protein hydrolyzate component, wherein the amount of lactose added is 15% to 300% by mass of the whey protein content; In the step of inactivating the enzyme, after the hydrolysis is completed, the pH value of the hydrolyzate solution is adjusted to 7.2-8.0 and then heated to inactivate the enzyme. [2] The method according to [1], wherein in the hydrolysis step, the solid content of the whey protein aqueous solution is The whey protein aqueous solution has a carbohydrate content of 10% by mass or less, based on the dry weight of solids. [3] The method according to [1] or [2], wherein the enzyme is a complex enzyme of an endoprotease and an exoprotease. [4] The method according to any one of [1] to [3], wherein the pH of the hydrolysis system in the hydrolysis step is 6.5 to 7.5. [5] The method according to any one of [1] to [4], wherein in the step of inactivating the enzyme, the temperature of heating to inactivate the enzyme is 105 to 110°C and the time is less than 30 seconds. [6] The method according to any one of [1] to [5], wherein the method further comprises a concentration step after the enzyme inactivation step. [7] The method according to [6], wherein in the concentration step, the hydrolyzate solution after enzyme inactivation is concentrated to a solid content higher than 35% by mass. [8] The method according to any one of [1] to [7], wherein lactose is added to the hydrolysis system 4 to 8 minutes before the end of the hydrolysis. [9] The method according to any one of [1] to [8], wherein the content of protein components with a molecular weight of 3000 Da or less in the whey protein product obtained by the method is greater than 75% of the total protein.

[0010] .Furthermore, the present invention also provides a method for preparing infant formula milk powder, wherein the method comprises the method for preparing a whey protein product according to any one of [1] to [9] above. Effects of the Invention By implementing the above technical solution, the present invention can achieve the following technical effects: 1) The method of the present invention does not require preheating and modification of the whey protein raw material or whey protein solution before hydrolysis, which can further alleviate the influence of thermal denaturation on whey protein hydrolysis and the quality of the final product; 2) In the present invention, lactose is added before the hydrolysis process is completed, so that the lactose performs glycosylation modification on the hydrolyzate of whey protein, which not only improves the stability of the hydrolyzate, is beneficial for resisting high temperature thermal denaturation during subsequent spray drying, but also increases the solubility of the hydrolyzate; 3) pH protection is used during the enzyme inactivation process to adjust the pH of the enzymatic solution to a range of 7.2 to 8.0, ensuring that the enzymatic solution is uniform and non-denatured while inactivating the enzyme; 4) Through the above method, not only a spray-dryable solution with a higher concentration is obtained after the concentration treatment, but the obtained spray-dried powder also has good dissolution properties; 5) The method of the present invention not only greatly improves the production efficiency, but also can obtain a high-quality hydrolyzed whey protein product, which is particularly suitable for preparing infant formula milk products. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1: Photograph of the protein component after enzyme inactivation in Example 1; Figure 2: Photograph of the protein component after enzyme inactivation in Comparative Example 1; Figure 3: HPLC chromatogram of the product prepared in Example 2. DETAILED DESCRIPTION Various exemplary embodiments, features and aspects of the present invention will be described in detail below. In order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production. In this specification, the word "may" means both performing a certain process and not performing a certain process. In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B. In the present invention, a numerical range expressed using "above" or "below" means a numerical range including the number. In the present invention, the use of "optional" or "optionally" indicates that certain substances, components, execution steps, applied conditions and other factors are used or not used. In the present invention, "Da" is used to represent the unit of molecular weight "Dalton", that is, "Dalton". In the present invention, unless otherwise specified, the "normal temperature" used generally refers to a temperature of 23±2°C. In the present invention, unless otherwise stated, "%" used herein means weight or mass percentage. In the present invention, a mixed system of milk powder and water is used as a "solution", which may be a substantial microemulsion system. In this specification, "infants" are used to refer to a human group under the age of 3 years old. In this specification, for the convenience of describing fatty acid glycerides, the following characters are used to refer to different types of fatty acids: Ca: capric acid (C10:0); La: lauric acid (C12:0); M: myristic acid (C14:0); P: palmitic acid (C16:0); S: stearic acid (C18:0); O: oleic acid (C18:1); L: linoleic acid (C18:2); Ln: linolenic acid (C18:3). In this specification, for specific fatty acid esters, the above-mentioned characters are used in parallel combination to indicate the type of fatty acid glyceride, wherein the letter or letter combination in the middle position indicates the fatty acid at the 2nd position of glycerol. For example: OPO is used to represent 1,3-dioleoyl-2-palmitoylglycerol triglyceride; OPL is used to represent 1-oleoyl-2-palmitoyl-3- Linoleic acid triglycerides. In this specification, the terms "substantially" and "essentially" may mean that a value includes the standard deviation of the error of the device or method used to determine the value. The numerical ranges and parameters used to define the present invention are approximate values, and the relevant values ​​in the specific embodiments have been presented as accurately as possible. However, any numerical value inherently inevitably contains the standard deviation caused by the aforementioned testing device or method. In the present invention, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner. The present invention primarily provides a method for hydrolyzing whey protein, which comprises hydrolyzing a whey protein solution in the presence of an enzyme, and adding lactose at the end of the hydrolysis reaction. The enzyme is further inactivated under a specific pH condition, and then concentrated and spray-dried to obtain a hydrolyzed whey protein solid powder. The present invention is mainly based on the following insights: The present invention is different from the pre-(heat) modification method in the prior art. The whey protein raw material or whey protein solution of the present invention does not need to be pre-modified by heating. In addition, it has been found that when whey protein is hydrolyzed in the presence of an enzyme, lactose is added to make the whey protein hydrolyzate glycosylated, thereby increasing the heat stability and solubility of the hydrolyzate, thereby increasing the solid content of the solution during spray drying and inhibiting the denaturation effect of high temperature on the protein component. In addition, by adjusting the pH value of the system to an appropriate range during enzyme inactivation, the adverse effects of high temperature treatment on protein components can be alleviated. Specifically, the method for hydrolyzing whey protein of the present invention mainly comprises a step of hydrolysis in the presence of an enzyme, a step of inactivating the enzyme, and other optional post-treatment steps. (Whey Protein) In principle, the source of the whey protein used as a raw material in the present invention is not particularly limited. For example, the whey protein may be derived from various animal milks, such as cow's milk, goat's milk, horse's milk, camel's milk, etc. Preferably, it may be derived from cow's milk. There is no particular limitation on the method for separating or purifying whey from the animal milk. In some specific embodiments, the separation or purification means includes a defatting process to separate the fat component from the animal milk raw material. In principle, there is no particular limitation on the defatting method, which can be performed by centrifugation or the like. By defatting, at least 90% by mass, preferably 92% by mass, and more preferably 95% by mass of the total fat in the animal milk raw material is removed. More than % by mass of fat is separated. In some specific embodiments, the above separation or purification also includes separating proteins from the raw milk (which has been defatted). For the separation of proteins, the casein therein is mainly separated. There is no particular limitation on the method for separating casein. For example, the pH of the raw milk can be adjusted by adding an acidic substance to cause the casein to condense and precipitate near its isoelectric point, thereby separating (acid whey); or, by optionally adding coagulants, leavening agents and other ingredients to the raw milk, the whey component (sweet whey) is separated while the cheese is formed. In addition, in some other specific embodiments, membrane filtration can also be used to intercept and separate protein components of different molecular weights through the use of a filter membrane with a suitable pore size, thereby obtaining a whey protein raw material of the present invention with different components. More specifically, in the step of above-mentioned isolated whey protein, for example, the steps of desalting and concentrating can be included. That is, after defatting and protein separation, the composition enriched with whey protein can be desalted and optionally concentrated. For the processing of desalting, there is no particular restriction in principle, for example, modes such as membrane filtration (nanofiltration (NF) and / or electrodialysis) can be used to carry out. In some preferred embodiments, by desalting, inorganic salts more than 70 mass %, preferably more than 80 mass %, more preferably more than 90 mass % can be removed. For the step of concentrating, it can be carried out while or after desalting, and typically ultrafiltration, diafiltration or reverse osmosis can be used to obtain a whey protein raw material with a higher protein content. The whey protein-containing components obtained by the above-mentioned possible various process treatments can be further dried to obtain whey protein solids. Typically, solid whey protein powder can be obtained by spray drying or the like. In addition, the whey protein raw material of the present invention can be prepared by the above method or purchased through commercial channels, such as various commercially available concentrated whey protein powders, isolated whey protein powders, whey protein liquids and other high whey protein content raw materials. Preferably, the whey protein raw material of the present invention can use isolated whey protein. There is no particular limitation on the content of whey protein in the whey protein raw material of the present invention, which is related to the preparation method of the whey protein raw material. In some specific embodiments, the whey protein content in the whey protein raw material (based on the total dry weight of the whey protein raw material) can be 50% by weight or more, preferably 60-95% by weight, for example 65-90% by weight, 70-85% by weight, etc. Further, in addition to containing whey protein, the whey protein raw material of the present invention may also contain one or more of carbohydrates, oil components and inorganic salts. Carbohydrates may include polysaccharides, such as lactose or dietary fiber. In some specific embodiments, according to different purification methods of whey protein, the (dry) content of the carbohydrates is less than 10% by mass, preferably less than 8% by mass, for example, 1-7% by mass, 2-6% by mass, etc., based on the total dry weight of the whey protein raw material. In some other preferred embodiments, the lactose in the whey protein can be controlled to a lower content range, which can be achieved by the above-mentioned separation and purification. Based on the total dry weight of the whey protein raw material, the lactose (dry) content is less than 8% by mass, preferably less than 5% by mass, for example, 1-4% by mass, 2-3% by mass, etc. In addition, the whey protein raw material of the present invention may be a whole protein raw material that has not been subjected to any degradation treatment, or a whey protein raw material that has been subjected to a partial degradation treatment but can still be further degraded as described below to reach the desired composition of the present invention. Further, after obtaining the above-mentioned whey protein raw material, it can be mixed with water before the hydrolysis described below to form a whey protein aqueous solution. In some preferred embodiments, for the whey protein aqueous solution, from the perspective of being conducive to the sufficient hydrolysis described below, its solid content can be less than 18% by mass, for example, 5 to 16% by mass, 8 to 13% by mass, etc. For the whey protein raw material of the present invention, the heat experience experienced by the whey protein raw material after it is separated from animal milk (such as solid (powder)) or the formed whey protein aqueous solution before hydrolysis does not exceed 40°C, and the preferred heat experience temperature is 20-35°C. (Hydrolyzed Whey Protein) The hydrolysis of whey protein in the present invention is enzymatic hydrolysis performed in the presence of an enzyme. In principle, there is no particular limitation on the enzymes that can be used in the present invention. In some specific embodiments of the present invention, these enzymes can be selected from one or more of various endoproteases or exoproteases. For the endoproteases that can be used in the present invention, one or more of papain, alkaline protease, trypsin, pepsin, acid protease, neutral protease, and composite protease (Protamex1.6) can be listed; for the exoproteases that can be used, in some specific embodiments, one or more of protein deamidase, flavor protease (Flavourzyme 500MG), aminopeptidase, and carboxypeptidase are included. For these enzymes, they can be obtained commercially, for example, they can be commercially available from Novozymes, Amano, DSM and other companies. From the perspective of hydrolysis efficiency and avoiding or inhibiting the bad taste (bitterness, etc.) caused by the exposure of the terminal amine group, etc., the enzyme available in the present invention can be a composite enzyme including an endoprotease and an exoprotease. More preferably, the composite enzyme can be a composite enzyme formed by combining the above-mentioned mixed protease as an endoprotease and a flavor protease as an exoprotease. For the amount of the composite enzyme, in some preferred embodiments, the mass ratio of endoprotease to exoprotease can be 1.5-2.5:2.5-3.5. Further, the total amount of the above-mentioned (compounded) enzyme is not particularly limited in principle and can be determined according to the conventional amount corresponding to the characteristics of each enzyme in the art. In some preferred embodiments, the total amount of the enzyme can be The whey protein is used in an amount of 1 to 4% by mass, for example, 1.6 to 3% by mass, based on the amount of whey protein (dry weight). In addition, other conditions for the hydrolysis are not particularly limited in principle, and buffering components can be used to adjust the pH value of the whey protein solution system according to the conditions such as the enzyme used, for example, the pH is adjusted to 6.8 to 7.2. There is no particular limitation on the type of such buffering components in principle, as long as it complies with the provisions of food safety laws and regulations. Typically, one or more of alkali metal carbonates, bicarbonates, phosphates, (mono- or di-) hydrogen phosphates or alkali metal hydroxides can be cited. Furthermore, the hydrolysis temperature may be not more than 55° C., preferably 45 to 55° C., such as 48° C., 50° C., etc. In addition, the hydrolysis time may be 0.5 to 1 hour, preferably 0.7 to 1 hour. In the above-mentioned hydrolysis process, it has been found that the addition of lactose can promote the glycosylation reaction of the whey protein hydrolysate. As a result of such a reaction, not only the heat stability of the hydrolysate can be improved, but also the water solubility of the hydrolysate can be improved, and the solid content of the solution during spray drying described below can be significantly increased. In particular, due to the addition of lactose in the hydrolysis of the present invention, a whey protein hydrolysate with better solubility can be obtained in a shorter time. Regarding the amount of lactose added, in some preferred embodiments, from the perspective of fully carrying out the glycosylation reaction, the amount of lactose added (based on dry weight) is 15% to 300% by mass of the total amount of whey protein components in the whey protein aqueous solution, preferably 20% to 250% by mass, more preferably 30% to 200% by mass, for example 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, 120%, 150%, 170% by mass, etc. In addition, there is no particular limitation on the timing of adding the lactose as long as it is after the appropriate hydrolyzate is generated. For example, in some specific embodiments, the entire hydrolysis process (from heating to the start of the hydrolysis temperature to the stop of heating) can be divided into three equal time periods. Therefore, lactose can be added after the start of the third time period (i.e., the final hydrolysis time period); in other specific embodiments, lactose can also be added within 3 to 8 minutes before the end of hydrolysis (stop of hydrolysis heating), for example, the above amount of lactose can be added 4 minutes, 5 minutes or 6 minutes before the end of hydrolysis. After adding lactose, optionally, auxiliary measures such as stirring can be used to promote the occurrence of glycosylation reaction in the mixed system. In addition, in some preferred embodiments, the glycosylation reaction time is at least 4 minutes, such as 4 to 10 minutes. In addition, there is no particular limitation on the total hydrolysis degree of whey protein in the hydrolysis treatment of the present invention, and it can typically be 8 to 16% (OPA test). (Enzyme inactivation) After the enzymatic hydrolysis is completed, the whey protein hydrolysate can be subjected to enzyme inactivation treatment. It has been proved in the present invention that the proper adjustment of the pH value of the hydrolyzate solution can effectively inhibit the thermal denaturation of protein components caused by high temperature treatment during the enzyme inactivation process. In some specific embodiments, the pH value of the hydrolyzate solution can be adjusted to 7.2 to 8.0, preferably 7.5 to 7.8, and then heated to inactivate the enzyme. There is no particular limitation on the method for adjusting the pH value, for example, various water-soluble alkaline components, such as one or more of alkali metal hydroxides, can be used. If the pH value is too low, the protein component cannot be protected during the inactivation of the enzyme, and if the pH value is too high, more alkaline components will need to be introduced, resulting in excessive ash content in the final product. There is no particular limitation on the enzyme inactivation treatment. For example, a high temperature inactivation method can be used. In some specific embodiments, the enzyme inactivation temperature can be 105-110°C, and the enzyme inactivation time can be no more than 30 seconds, preferably 10-25 seconds. (Other steps) The whey protein hydrolysis method of the present invention may optionally include a sterilization step, a concentration step, a drying step, etc. in addition to the above-mentioned hydrolysis step and enzyme inactivation step. The sterilization step can be performed at any desired time after the enzyme is inactivated. In some preferred embodiments, steam injection sterilization (DSI) can be used, and the sterilization temperature can be controlled at 75-80° C. and the sterilization time can be 10-20 seconds. For the concentration step, an evaporation concentration method can be used. In some specific embodiments, a triple-effect evaporator can be used to concentrate the system after enzyme inactivation (and sterilization). In addition, for the solution system obtained after concentration, its solid content can be 35% by mass or more, preferably 36% to 45% by mass, and more preferably 37% to 42% by mass. Since the glycosylation modification reaction described above leads to an increase in the solubility of the hydrolyzate, the solid content of the concentrate of the present invention can be significantly improved compared to the previous method. For the drying step, spray drying can be typically used to obtain a solid powdered whey protein hydrolyzate product. There is no particular restriction on the temperature, pressure and other conditions of spray drying, and the conventional operating specifications in the art can be referred to. (Whey protein products) The whey protein product of the present invention is the hydrolyzed whey protein product described above, which can preferably be in the form of a solid (powder) or can be configured as an aqueous solution for further use. In some preferred embodiments, the whey protein product of the present invention has the following molecular weight distribution: (i) The content of protein components with a molecular weight of 3000 Da or less in the whey protein product is 75% by mass of the total protein It is 77% by mass or more, preferably 79% by mass or more, and more preferably 79% by mass or more. And optionally, it can also have the following molecular weight distribution: (ii) The content of protein components having a molecular weight of more than 3,000 Da and less than 10,000 Da in the whey protein product is 3% by mass to 10% by mass. Furthermore, the whey protein product of the present invention is particularly suitable for the preparation of infant formula milk products, and the ash content thereof is 5.5% by mass or less. In other specific embodiments, the content of protein components (protein / peptide / amino acid) in the whey protein product of the present invention is 25% by mass or more, preferably 30% by mass or more, and the content is calculated based on the total dry weight of the product. (Formulated dairy products) Furthermore, the present invention also provides a method for preparing a formula milk product. Since the whey protein product of the present invention is added or used in the method, the method also includes the method for preparing the whey protein product of the present invention. For the formula milk product, the following components can be mixed according to the preparation method of formula milk powder in the prior art: Specifically, the components of the formula milk product of the present invention may include: (A) The whey protein product of the present invention, and one or more of the following additional components (i.e., these components do not come from the whey protein product): (B) functional protein component, (C) carbohydrate component, (D) oil component, (E) mineral salt component, (F) vitamin component / probiotic component. Functional protein ingredients There is no particular restriction on the functional protein components that can be used in principle, such as various caseins, immunoglobulins, lactoferrin, and other whey proteins other than the above-mentioned whey proteins. There is no particular restriction on the amount of these components added, as long as they comply with the provisions of laws and regulations. These protein components can be directly derived from animal milk, such as (raw) cow's milk, or a separate purified protein component. Carbohydrate content There is no particular limitation on the type or source of the carbohydrate components added to the formula milk product of the present invention in principle, and the carbohydrates commonly used in the formula milk powder products for the middle-aged and elderly in the art can be used. In some specific embodiments, the carbohydrate component of the present invention mainly refers to sugar substances. The sugar substances are generally a general term for polyhydroxy aldehydes or polyhydroxy ketones and their polycondensates and certain derivatives, generally composed of carbon, Composed of three elements, hydrogen and oxygen, sugar substances can be written as empirical molecular formulas: C n (H 2 O) n . In the present invention, the carbohydrate substances may typically include monosaccharides, disaccharides, polysaccharides or oligosaccharides. Monosaccharides mainly include glucose, fructose and the like. Disaccharides, polysaccharides or oligosaccharides may include: sucrose, lactose, nitrosacetose, nitrotetrose, nitrosacetose, oligofructose, glucosaminoglycans, (malto)dextrin, and various forms of human milk oligosaccharides. In addition, the carbohydrates may also be added in the form of dietary fiber. For dietary fiber substances, for example, one or more of inulin, konjac flour, galacto-oligosaccharides, fructo-oligosaccharides, isomalto-oligosaccharides, soybean polysaccharides, cyclodextrin, resistant dextrin, and soybean fiber may be cited. Furthermore, there is no particular limitation on the total content of carbohydrate components in the formula milk product of the present invention, and the total content of carbohydrate components can be prepared with reference to the carbohydrate content in formula milk products commonly used for specific groups of people, such as infants and young children, in the art. Oil composition There is no particular limitation on the type of the oil component added to the formula dairy product of the present invention in principle, and fatty acid glycerides commonly used in the art can be used. For these glycerides, it can be obtained by extracting from plants or by artificial synthesis (transesterification). For transesterification method, glycerol and fatty acid can be carried out esterification reaction in the presence of a catalyst, or triglyceride and fatty acid in existing various sources can be carried out transesterification reaction in the presence of a (specific) catalyst (enzyme) to obtain. For the vegetable oil extracted from plants, required fatty acid glyceride can be obtained by mixing one or more vegetable oils extracted below. The vegetable oil includes one or more of rapeseed oil, soybean oil, sunflower seed oil, olive oil, sesame oil, corn oil, linseed oil, and camellia oil. For fatty acid glyceride of the present invention, mainly triglyceride. For these glycerides, for example OPL, OPO, MLCT, OOL, OPP, OLO, OLL, LPL, LPLn, OPLn, LPCa, OPCa etc. can be listed. The so-called "MLCT structured mixed ester" is a structural mixed ester with medium- and long-chain fatty acid triglycerides as the main components. "MLCT" refers to medium to long chain triglycerides, which are structural esters containing both medium-chain fatty acids (M) and long-chain fatty acids (L) on the glycerol skeleton, where medium-chain fatty acids refer to fatty acids containing 6 to 12 carbon atoms, and long-chain fatty acids refer to fatty acids with more than 12 carbon atoms. MLCT has the characteristics of both medium and long-chain fatty acids, and has the characteristics of supplementing essential fatty acids, quickly supplying energy and not causing fat accumulation. Common MLCTs are mainly OPLa, LPLa, OPCa, OLaO, OLaL, OMLa, SLaL and SLaO. Mineral salt ingredients The mineral salt components that can be added to the formula dairy product of the present invention are mainly used to introduce calcium or other trace nutrients, such as iron, copper, manganese, zinc, cobalt, molybdenum, chromium, nickel, vanadium, fluorine, selenium, iodine, silicon, tin, etc. Furthermore, the content of mineral salts in formula dairy products only needs to comply with the provisions of laws and regulations. Other nutritional supplement ingredients There is no particular limitation on other nutritional supplement ingredients that can be added to the formula dairy product of the present invention, and they can be prepared according to existing methods in the art. In some specific embodiments, the supplement ingredients include: one or more selected from vitamins and probiotics. Vitamins include vitamin A, beta-carotene, vitamin D 3 , Vitamin E, Vitamin K 1 , Vitamin B 1 , Vitamin B 2 , Vitamin B 6 , Vitamin B 12 , vitamin C, pantothenic acid, folic acid, niacin, and biotin. The probiotics may be, for example, bifidobacteria that are beneficial to the gastrointestinal tract. In addition, there is no particular limitation on the source of each component (B) to (F) above, and they can be introduced by, for example, mixing with animal milk or other nutritional supplements. Furthermore, the above-mentioned formula milk products of the present invention are, in principle, suitable for various groups of people through adjustment of composition, but in some specific embodiments, they are particularly suitable for formula milk products for infants and young children. Example The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the raw materials or instruments used do not specify the manufacturer, they are all conventional products that can be obtained commercially. Example 1 Hydrolyzed whey protein powder, obtained by: Step 1: Mix concentrated whey protein powder WPC80 with a certain amount of pure water to prepare a protein solution with a mass concentration of 10%, and heat the obtained protein solution to 50±2°C; Step 2: Use KOH solution to adjust the pH of the protein solution to 7.0±0.2, add composite protease (Protamex1.6, 1.6AU-N / g) and flavor protease (Flavourzyme 500MG, 500LAPU / g), the added amount is 2.5% of the substrate protein content, and the ratio of composite protease to flavor protease is 2:3, and stir and hydrolyze at 50±2°C for 40 minutes; Step 3: 5 minutes before the end of hydrolysis, add lactose in a ratio of protein: lactose = 1:0.5, continue stirring and dissolving for 5 minutes, and after the hydrolysis is completed, use KOH solution to adjust the pH of the liquid to 7.2 and inactivate the enzyme at 105°C for 20 seconds; Step 4: The enzyme-killing liquid is concentrated by triple-effect evaporation, with a preheating temperature of 50°C, a DSI sterilization temperature of 80°C, a time of 15s, a first-effect body temperature of 70°C, a second-effect body temperature of 60°C, a third-effect body temperature of 50°C, and a discharge liquid concentration of 35%; Step 5: The feed concentration of the spray drying is the same as the discharge concentration of the evaporator, the feed preheating temperature is 60°C, the inlet air temperature is 200°C, and the exhaust air temperature is 85°C. Example 2 Hydrolyzed whey protein powder, obtained by: Step 1: Mix concentrated whey protein powder WPC80 with a certain amount of pure water to prepare a protein solution with a mass concentration of 10%, and heat the obtained protein solution to 50±2°C; Step 2: Use KOH solution to adjust the pH of the protein solution to 7.0±0.2, add composite protease (Protamex1.6, 1.6AU-N / g) and flavor protease (Flavourzyme 500MG, 500LAPU / g), the added amount is 2.5% of the substrate protein content, and the ratio of composite protease to flavor protease is 2:3, and stir and hydrolyze at 50±2°C for 40 minutes; Step 3: 5 minutes before the end of hydrolysis, add lactose in a ratio of protein: lactose = 1:0.5, continue stirring and dissolving for 5 minutes, and after the hydrolysis is completed, use KOH solution to adjust the pH of the liquid to 7.5 and then inactivate the enzyme at 105°C for 20 seconds; Step 4: The enzyme-killing liquid is concentrated by triple-effect evaporation, with a preheating temperature of 50°C, a DSI sterilization temperature of 80°C, a time of 15s, a first-effect body temperature of 70°C, a second-effect body temperature of 60°C, a third-effect body temperature of 50°C, and a discharge liquid concentration of 38%; Step 5: The feed concentration of spray drying is the same as the discharge concentration of evaporator, the feed preheating temperature is 60°C, the inlet air temperature is 200°C, and the exhaust air temperature is 88°C. Example 3 Hydrolyzed whey protein powder, obtained by: Step 1: Mix concentrated whey protein powder WPC80 with a certain amount of pure water to prepare a protein solution with a mass concentration of 10%, and heat the obtained protein solution to 50±2°C; Step 2: Use KOH solution to adjust the pH of the protein solution to 7.0±0.2, add composite protease (Protamex1.6, 1.6AU-N / g) and flavor protease (Flavourzyme 500MG, 500LAPU / g), the added amount is 2.5% of the substrate protein content, and the ratio of composite protease to flavor protease is 2:3, and stir and hydrolyze at 50±2°C for 40 minutes; Step 3: 5 minutes before the end of hydrolysis, add lactose in a ratio of protein: lactose = 1:0.5, continue stirring and dissolving for 5 minutes, and after the hydrolysis is completed, use KOH solution to adjust the pH of the liquid to 8.0 and inactivate the enzyme at 105°C for 20 seconds; Step 4: The enzyme-killing liquid is concentrated by triple-effect evaporation, with a preheating temperature of 50°C, a DSI sterilization temperature of 80°C, a time of 15s, a first-effect body temperature of 70°C, a second-effect body temperature of 60°C, a third-effect body temperature of 50°C, and a discharge liquid concentration of 38%; Step 5: The feed concentration of the spray drying is the same as the discharge concentration of the evaporator, the feed preheating temperature is 60°C, the inlet air temperature is 200°C, and the exhaust air temperature is 88°C. Example 4 Step 1: Mix concentrated whey protein powder WPC80 with a certain amount of pure water to prepare a protein solution with a mass concentration of 10%, and heat the obtained protein solution to 50±2°C; Step 2: Use KOH solution to adjust the pH of the protein solution to 7.0±0.2, add composite protease (Protamex1.6, 1.6AU-N / g) and flavor protease (Flavourzyme 500MG, 500LAPU / g), the added amount is 2.5% of the substrate protein content, and the ratio of composite protease to flavor protease is 2:3, and stir and hydrolyze at 50±2°C for 40 minutes; Step 3: 5 minutes before the end of hydrolysis, add lactose in a ratio of protein: lactose = 1:0.2, continue stirring and dissolving for 5 minutes, and after the hydrolysis is completed, use KOH solution to adjust the pH of the liquid to 7.5 and inactivate the enzyme at 105°C for 20 seconds; Step 4: The enzyme-killing liquid is concentrated by triple-effect evaporation, with a preheating temperature of 50°C, a DSI sterilization temperature of 80°C, a time of 15s, a first-effect body temperature of 70°C, a second-effect body temperature of 60°C, a third-effect body temperature of 50°C, and a discharge liquid concentration of 35%; Step 5: The feed concentration of the spray drying is the same as the discharge concentration of the evaporator, the feed preheating temperature is 60°C, the inlet air temperature is 200°C, and the exhaust air temperature is 85°C. Example 5 Step 1: Mix concentrated whey protein powder WPC80 with a certain amount of pure water to prepare a protein solution with a mass concentration of 10%, and heat the obtained protein solution to 50±2°C; Step 2: Use KOH solution to adjust the pH of the protein solution to 7.0±0.2, add composite protease (Protamex1.6, 1.6AU-N / g) and flavor protease (Flavourzyme 500MG, 500LAPU / g), the added amount is 2.5% of the substrate protein content, and the ratio of composite protease to flavor protease is 2:3, and stir and hydrolyze at 50±2°C for 40 minutes; Step 3: 5 minutes before the end of hydrolysis, add lactose in a ratio of protein: lactose = 1:3, continue stirring and dissolving for 5 minutes, and after the hydrolysis is completed, use KOH solution to adjust the pH of the liquid to 7.5 and then inactivate the enzyme at 105°C for 20 seconds; Step 4: The enzyme-killing liquid is concentrated by triple-effect evaporation, with a preheating temperature of 50°C, a DSI sterilization temperature of 80°C, a time of 10-20s, a first-effect body temperature of 70°C, a second-effect body temperature of 60°C, a third-effect body temperature of 50°C, and a discharge liquid concentration of 45%; Step 5: The feed concentration of spray drying is the same as the discharge concentration of evaporator, the feed preheating temperature is 40-70℃, the inlet air temperature is 190℃, and the exhaust air temperature is 90℃. Comparative Example 1 Step 1: Mix concentrated whey protein powder WPC80 with a certain amount of pure water to prepare a protein solution with a mass concentration of 10%, and heat the obtained protein solution to 50±2°C; Step 2: Use KOH solution to adjust the pH of the protein solution to 7.0±0.2, add composite protease (Protamex1.6, 1.6AU-N / g) and flavor protease (Flavourzyme 500MG, 500LAPU / g), the added amount is 2.5% of the substrate protein content, and the ratio of composite protease to flavor protease is 2:3, and stir and hydrolyze at 50±2°C for 40 minutes; Step 3: 5 minutes before the end of hydrolysis, add lactose in a ratio of protein: lactose = 1:0.5, continue stirring and dissolving for 5 minutes, and after the hydrolysis is completed, use KOH solution to adjust the pH of the liquid to 7.0 and inactivate the enzyme at 105°C for 20 seconds; Comparative Example 1 was compared with Example 1. In step 3, the pH of Comparative Example 1 was adjusted to 7.0 after hydrolysis to inactivate the enzyme. After inactivation of the enzyme, it was found that the protein in Comparative Example 1 was severely denatured, as shown in FIG2 , while the protein in Example 1 was not denatured, as shown in FIG1 . Comparative Example 2 Step 1: Mix concentrated whey protein powder WPC80 with a certain amount of pure water to prepare a protein solution with a mass concentration of 10%, and heat the obtained protein solution to 50±2°C; Step 2: Use KOH solution to adjust the pH of the protein solution to 7.0±0.2, add composite protease (Protamex1.6, 1.6AU-N / g) and flavor protease (Flavourzyme 500MG, 500LAPU / g), the added amount is 2.5% of the substrate protein content, and the ratio of composite protease to flavor protease is 2:3, and stir and hydrolyze at 50±2°C for 40 minutes; Step 3: 5 minutes before the end of hydrolysis, add lactose in a ratio of protein: lactose = 1:0.5, continue stirring and dissolving for 5 minutes, and after the hydrolysis is completed, use KOH solution to adjust the pH of the liquid to 8.2 and then inactivate the enzyme at 105°C for 20 seconds; Step 4: The enzyme-killing liquid is concentrated by triple-effect evaporation, with a preheating temperature of 50°C, a DSI sterilization temperature of 80°C, a time of 15s, a first-effect body temperature of 70°C, a second-effect body temperature of 60°C, a third-effect body temperature of 50°C, and a discharge liquid concentration of 40%; Step 5: The feed concentration of spray drying is the same as the discharge concentration of evaporator, the feed preheating temperature is 60℃, the inlet air temperature is 190℃, and the exhaust air temperature is 90℃. In Comparative Example 2, when the pH of the liquid to be inactivated was adjusted to 8.2, although the liquid was stable after the enzyme was inactivated, the amount of KOH added was large, and the final product test results showed that the ash content was 6.2%, exceeding the national standard requirement of ≤5.5%, and could not be used for infant formula production. Comparative Example 3 Step 1: Mix concentrated whey protein powder WPC80 with a certain amount of pure water to prepare a protein solution with a mass concentration of 10%, and heat the obtained protein solution to 50±2°C; Step 2: Use KOH solution to adjust the pH of the protein solution to 7.0±0.2, add composite protease (Protamex1.6, 1.6AU-N / g) and flavor protease (Flavourzyme 500MG, 500LAPU / g), the added amount is 2.5% of the substrate protein content, and the ratio of composite protease to flavor protease is 2:3, and stir and hydrolyze at 50±2°C for 40 minutes; Step 3: 5 minutes before the end of hydrolysis, add lactose in a ratio of protein: lactose = 1:0.1, continue stirring and dissolving for 5 minutes, and after the hydrolysis is completed, use KOH solution to adjust the pH of the liquid to 7.5 and then inactivate the enzyme at 105°C for 20 seconds; Step 4: The enzyme-killing liquid is concentrated by triple-effect evaporation, with a preheating temperature of 50°C, a DSI sterilization temperature of 80°C, a time of 15s, a first-effect body temperature of 70°C, a second-effect body temperature of 60°C, a third-effect body temperature of 50°C, and a discharge liquid concentration of 22%; Step 5: The feed concentration of spray drying is the same as the discharge concentration of evaporator, the feed preheating temperature is 40-70℃, the inlet air temperature is 200℃, and the exhaust air temperature is 80℃. In step 3 of comparative example 3, 5 minutes before the end of hydrolysis, lactose was added in a ratio of protein: lactose = 1:0.1. In step 4, the solid content of the concentrated solution outlet concentration could only reach 22%. When the concentration was further increased, the fluidity of the concentrated solution deteriorated and showed a gel tendency, which was not conducive to the flow of the solution in the evaporator. The spray-dried product obtained in step 5 had fine particles, poor dissolution, and a product yield of 71%, which was low. Comparative Example 4 Step 1: Mix concentrated whey protein powder WPC80 with a certain amount of pure water to prepare a protein solution with a mass concentration of 10%, and heat the obtained protein solution to 50±2°C; Step 2: Use KOH solution to adjust the pH of the protein solution to 7.0±0.2, add composite protease (Protamex1.6, 1.6AU-N / g) and flavor protease (Flavourzyme 500MG, 500LAPU / g), the added amount is 2.5% of the substrate protein content, and the ratio of composite protease to flavor protease is 2:3, and stir and hydrolyze at 50±2°C for 40 minutes; Step 3: 5 minutes before the end of hydrolysis, add lactose in a ratio of protein: lactose = 1:3.1, continue stirring and dissolving for 5 minutes, and after the hydrolysis is completed, use KOH solution to adjust the pH of the liquid to 7.5 and then inactivate the enzyme at 105°C for 20 seconds; Step 4: The enzyme-killing liquid is concentrated by triple-effect evaporation, with a preheating temperature of 50°C, a DSI sterilization temperature of 80°C, a time of 15s, a first-effect body temperature of 70°C, a second-effect body temperature of 60°C, a third-effect body temperature of 50°C, and a discharge liquid concentration of 45%; Step 5: The feed concentration of spray drying is the same as the discharge concentration of evaporator, the feed preheating temperature is 40-70℃, the inlet air temperature is 185℃, and the exhaust air temperature is 85℃. In Comparative Example 4, the spray-dried product obtained was in good condition, but the protein content of the obtained product was low, and the protein content of the final product was 23.8%, which was lower than the requirement of protein content ≥25% in GB11674. Application Example 1 The whey protein aqueous solution in the present invention is not subjected to pre-denaturation treatment. After hydrolysis according to the type and amount of the enzyme, the hydrolysis degree and molecular weight distribution of the obtained product are shown in Table 1. The high performance liquid chromatogram of the product prepared in Example 2 of the present invention is shown in Figure 3: Table 1: The hydrolysis time of the hydrolysis technology in the present invention is 40-60 minutes, which is 2-4 hours compared with the previous invention, greatly shortening the hydrolysis time and improving the production efficiency. Moreover, the hydrolysis degree and molecular weight distribution of the obtained product are also improved to a certain extent compared with the commercially available products. Application Example 2 The hydrolyzed whey protein powder prepared by the present invention and the conventional commercially available hydrolyzed whey protein powder were mixed into a solution with a mass concentration of 10%, and a sensory comparison was performed. The sensory evaluation method is as follows: (1) Bitterness evaluation: 10 g of each of three partially hydrolyzed whey protein powders (two commercially available products and one self-produced example 2) was weighed and dissolved in 90 mL of warm water at about 50° C., stirred thoroughly to dissolve, and provided as a mouthwash at the same temperature. Ten professional sensory evaluation personnel were invited to conduct comparative evaluation. (2) Wettability evaluation: Weigh 1 g of each of three partially hydrolyzed whey protein powders (two commercially available products and self-produced Example 2), and add 50°C distilled water to a 500 mL beaker. Pour the weighed milk powder into the beaker and start a stopwatch at the same time. Stop the stopwatch when all products are submerged in water and record the time taken. (3) White spot evaluation: Weigh 10 g of each of the three partially hydrolyzed whey protein powders (two commercially available products and self-produced Example 2), and dissolve them in 90 mL of warm water at about 50°C. Stir to fully dissolve them. After the reconstituted liquid poured into the beaker is left to stand for 1 minute, 3 / 4 of the clean microbiological slide is immersed in the reconstituted liquid and stirred vigorously for 5 seconds (do not make a circle). Take out the glass slide vertically, tilt it at about 60° for 10 seconds, and then tilt the back and bottom of the glass slide. Wipe dry. Compare against each other against a well-lit black background. (4) Solubility evaluation: After the white spot evaluation, the remaining reconstituted solution was allowed to stand for 30 min and the state of the liquid was observed. The sensory evaluation results are shown in Table 2 below: It should be noted that, although the technical solution of the present invention is introduced with specific examples, those skilled in the art will appreciate that the present invention should not be limited thereto. The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a whey protein product, characterized in that: The method comprises: The hydrolysis step and the enzyme inactivation step, in, In the hydrolysis step, the whey protein aqueous solution is hydrolyzed in the presence of an enzyme, the hydrolysis temperature is below 55° C., and the hydrolysis time is below 60 min. Furthermore, the whey protein aqueous solution is subjected to a heat treatment temperature not exceeding 40° C. before hydrolysis. Before the hydrolysis is completed, lactose is added to the system including the whey protein hydrolyzate component, wherein the amount of lactose added is 15% to 300% by mass of the whey protein content; In the step of inactivating the enzyme, after the hydrolysis is completed, the pH value of the hydrolyzate solution is adjusted to 7.2-8.0 and then heated to inactivate the enzyme.

2. The method according to claim 1, characterized in that In the hydrolysis step, the solid content of the whey protein aqueous solution is 18% by mass or less; and the carbohydrate content in the whey protein aqueous solution is 10% by mass or less based on the dry weight of solids.

3. The method according to claim 1 or 2, characterized in that: The enzyme is a composite enzyme of endoprotease and exoprotease.

4. The method according to any one of claims 1 to 3, characterized in that: The pH of the hydrolysis system in the hydrolysis step is 6.5 to 7.

5.

5. The method according to any one of claims 1 to 4, characterized in that: In the step of inactivating the enzyme, the temperature of heating to inactivate the enzyme is 105-110° C. and the time is less than 30 seconds.

6. The method according to any one of claims 1 to 5, characterized in that: The method further comprises a concentration step after the enzyme inactivation step.

7. The method according to claim 6, characterized in that In the concentration step, the hydrolyzate solution after the enzyme is inactivated is concentrated to a solid content of 35% by mass or more.

8. The method according to any one of claims 1 to 7, characterized in that: Lactose is added to the hydrolysis system within 4 to 8 minutes before the end of the hydrolysis.

9. The method according to any one of claims 1 to 8, characterized in that: In the whey protein product obtained by the method, the content of protein components with a molecular weight of less than 3000 Da accounts for more than 75% of the total protein.

10. A method for preparing infant formula milk powder, characterized in that: The method comprises the method for preparing a whey protein product according to any one of items 1 to 9.

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